1. Field of the Invention
This invention relates to a unit heater for heating large volume premises.
2. Description of Pertinent Information
Various types of unit heaters are known that essentially comprise a motor-ventilator unit that blows air through an expansion enclosure across which a heat exhanger extends. Such unit heaters are designed to heat large volume premises such as workshops, and usually are disposed horizontally. As a consequence, these unit heaters produce at their outlets substantially horizontal currents of hot air. As this hot air naturally tends to rise, the layers of air in the premises tend to stratify, resulting in very high temperature differentials between the ceiling of the premises and the floor. Such a difference in temperature may be on the order of 15.degree.-30.degree. C.
Unit heaters must furnish a quantity of heat greater than or equal to the quantity of heat lost to maintain a given comfortable temperature inside the premises. The heat loss is of two types: a static loss through the walls and ceiling, and a dynamic loss through renewal of the inside air. Due to stratification caused by the rise of hot air, heat losses through the roof of the premises are very considerable.
Currents of hot air are directed towards persons working in such premises to ensure their comfort to a desirable degree. Each person's feeling of comfort, however, depends upon the temperature of the ambient air, the air speed, the hygrometric degree of the air, and the rte of radiation of the walls and ceiling. People may feel cold even if hot air is blown onto them when working in the premises due to a combination of these factors. It is often necessary to increase the temperature of the air leaving the unit heater to compensate for these factors. As the temperature of the air is raised, however, the hotter air tends to rise and to stratify more quickly. Past attempts to overcome these drawbacks have involved providing accessories for raising air from the floor, but these accessories have the drawback of being expensive, cumbersome, and inefficient.
Another solution also has been envisaged, which consists of disposing the unit heaters vertically. The drawbacks mentioned above, concerning the direct blowing of air on people located in the premises to be heated, are again encountered with such an arrangement.